Method of assembling a circuit breaker



July 12, 1960 D. F. MOYER 2,944,324

METHOD OF ASSEMBLING A CIRCUIT BREAKER Original Filed Sept. 4, 1953 2 Sheets-Sheet 1 o l2 25 22 l5 '40 l8 7 I Fig. a 2 "l INVENTOR.

Dav/d FMoyer His Attorney July 12, 1960 D. F. MOYER METHOD OF ASSEMBLING A CIRCUIT BREAKER Original Filed Sept. 4, 1953 2 Sheets-Sheet 2 k V 72 r 74 so e1 l 62 Q 76 43 I L gi 63 64 f 65 Z as so Ll] 30 -|4 L 40 E42. m

l 52 INVENTOR.

David F. Mayer H/s Attorney United States to METHOD OF ASSEMBLING A CIRCUIT BREAKER David F. Moyer, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Original application Sept. 4, 1953, Ser. No. 378,555,

now Patent No. 2,743,335, dated Apr. 24, 1956. Divided and this application Feb. 14, 1956, Ser. No. 565,416

Claims. (Cl. 29-1555) This invention relates to a thermal control device, and

particularly to a small inexpensive thermostat for making and breakingelectric circuit in response to ambient temperature conditions, and a method of assembling and initially adjusting the thermal control device.

This application is a division of SN. 378,555, filed September 4, 1953, now Patent No. 2,743,335. 7

The device of this invention particularly concerns thermal control devices'of the bimetallic type wherein deflection of a bimetal member directly effects opening.

and closing of a pair of contacts, and even more specifically wherein a contact member is carried directly by a bimetal arm that deflects relative to-a second contact car- Further, when such a control device closes contacts,

the initial closing of the contact carried by the bimetallic arm upon the closing contact is at a time when very light contact pressure exists between the contacts. Here again the light contact pressure results in high contact resistance causing heating of the bimetal with resultant opening of the contacts. Such opening of the contacts causing cooling of the bimetal and reclosing of the contacts until such times as deflection of the bimetal is sufliciently strong to establish s'ufl'icient contact pressure upon closing of the contacts as will reduce the contact resistance sufliciently as to substantially eliminate the heating of the bimetal. Such operation of the thermal control device results in erratic control operations and a high degree of arcing of the contacts. I

It is therefore an object of this invention to provide a simplified structure of a thermal control device incorporating a direct acting contact carrying bimetallic arm which will eliminate the aforementioned difliculties-by effecting an increase of contact pressure at the time the contacts are opening or immediately after the initial closing of the contacts until the bimetallic arm has suflicient deflection under ambient temperature conditions to result in either a positive opening or closing of the contacts with resultant elimination of the contact resistance heating and normal deflection of the bimetallic member under response to ambient temperature conditions.

It is still another object of the invention to provide a thermal control device in accordance with the foregoing object wherein the bimetallic arm is provided'witli a return bend portion that carries a contact member, the return bend portion having less deflection in response toambienttemperature conditions than the main portion of the bimetallic arm to thereby render the bimetallic Patented July 12, 1960 arm sensitive only to ambient temperature responses but with the return bend portion being directly responsive to contact resistance heating to establish thereby increased contact pressure without effecting any substantial change in the responses of the main bimetallic arm to ambient temperature changes.

It is another object of the invention to provide a simplified structure of a direct acting bimetal thermal control device which is completely sealed and provided with an initial factory setting by deflection of the bimetal member under controlled conditions.

It is another object of the invention to provide a method to establish an initial factory adjustrnenton a direct acting bimetal thermal control device of the type referred to in the foregoing objects wherein the control device controls its own initial setting.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the invention is clearly shown.

In the drawings:

Figure l is a longitudinal cross sectional view of a thermal control device incorporating features of this invention.

Figure 2 is an end view of the device of Figure l, as viewed from theright hand end thereof. 1

Figure 3 is. a longitudinal cross sectional view similar to Figure l but illustrating the device under. certain conditions of operation.

Figure 4 is a transverse cross sectional view taken along lined-4 of Figure l.

Figure 5 is a transverse cross sectional View taken along line 5-5 of Figure 1.

Figure 6 is a schematic view of an apparatus providing a method for establishing initial factory adjustment of the thermal control device of this invention.

Referring to Figures 1 to 5, the thermal control device comprises a hollow casing 10 having a substantially rectangular chamber 11 therein. The end 12 of the casing is closed while the end 13 is open. A current conducting arm 14 is placed Within the chamber 11 and rests against the side 15 of the rectangllar opening in the casing 10.

The current conducting arm 14 has a contact portion 16 on one end thereofl The opposite end of the member 14 has a formed portion 17 that engages the end wall 18 of the casing 10 to control the entry of the arm 14 into the casing 10 and thus the position of the contact member 16 is controlled relative to the end 18 of the casing 16. A bimetal thermal control arm 20 is placed within the opening 11 of the casing 10. This arm 2%? has a formed portion 121 that engages the end wall 18 of the casing 10 to control the entry of the bimetal member 20 into the opening 11, and thus position the contact 21 on the end thereof in cooperating engagement with the contact 16 on the current conducting arm 14. The bimetal memher 20 is also a current conducting member.

The bimetal arm 20 has one end thereof provided with a return bend portion forming a leg portion 22 that is substantially shorter than the main bimetal leg portion 23. Since the bimetal member 20 is adapted to move the contact 21 from the contact 16 upon a rise in ambi ent temperature, the high expansion metal of the bimetal member 2%) will be on the side 24 thereof with the low expansion metal being on the side 124. Thus, the return bend leg portion 22 is adapted to deflect downwardly, as viewed in Figure 1, while the leg portion 23 deflects upwardly, in response to a rise in temperature.

. However, since the leg portion 22 has a total length that is substantially less than the total length of the leg 23, the degree of deflecting activity of the leg portion 22 in response to ambient temperature conditions will be substantially less than thedegree of deflection activity of the leg 23 in response to small rise in temperature such as that occurring in ambient temperatures surrounding the thermal control device. 'Thus, it can be said that the leg portion*22'is'substantially insensitive to rise in bient temperature to Which'the leg portion 23 of the bimetal 'rnember readily responds.

The bimetal "member 20 is of uniform thermal and physical characteristics from one end to the other thereof so that normal conduction of current through the bimetal member '20 will not affect its response to ambient "temperatureconditions. The bimetal member 20 is not a current-sensitive device, as this term is normally used, since thebimetal'20is adapted in this invention to carry the normal current load required ofthe device without sufficient 'heating of the bimetal as to *affect its response 'to'ambient' temperature conditions.

The bimetal member 20 and the current conducting arm 14, which is a temperature and current insensitive material, relatively speaking, are retained in position in the casing by means of a spacing member 25. The spacing member 25 frictionally engages the members 20 and 14 to hold them in engagement with the sides 15 and 26 respectively of the rectangular opening 11 in the casing 10. Also, the spacing member 25 provides means for establishing the initial opening point of the contact 21 from the contact 16 in a manner hereinafter described.

The bimetal member ztl has an angular portion 30 that is engaged by the spacer member 25 for the purpose of regulating the initial opening point of the contact 21 from the contact 16.

Assuming the thermal control device to have been assembled and properly adjusted, in a manner hereinafter described, the bimetal member 20 will therefore open contact 21 from contact 16 at a predetermined temperature upon a rise in temperature.

Since the movement of the bimetal 20 is a slow movement, the break between the contact 21 and the contact 16 is made extremely slow. Thus, a position of the bimetal 20. is reached at which the contact 21 barely touches the contact 16 with resulting loss of any substantial contact pressure between the contacts.

'This loss of contact pressure between the contacts 21 and 16 results in a high resistance being established between the contacts 21 and 16 which causes substantial heating. This heating resulting from contact resistance, is transmitted to the end portion 22 of the bimetal 20, and since the degree and rate of heat involved is substantially above that at which the ambient temperature is affecting the leg :portion 23 of the bimetal, the leg portion 22 of the bimetal will deflect downwardly, as viewed inFigure 1, to increase the pressure of the contact 21 upon the contact 16 and thereby substantially reduce the contact resistance between'the contacts. However, since the leg portion 22 is 'substantiallyshorter than the leg portion 23,:and substantial travel is required for the heat entering the leg22 to be transmitted to the leg 23 of the bimetal, and a :large dissipating'area isprovide'd in the leg portion 23, the legportion 23 of the bimetal 20 will be Isubstantially insensitive to the heat effect or the leg portion 22 of the bimetal 20.

Thus, the resistance heating of "the leg portion 22 provides deflection of this leg portion relative to the leg portion 23 to increase the contact resistance without any substantial 'efl ect on the responsiveness of the leg 23 of the :bimetal 20 to ambient temperatures.

With the leg portion '22 deflected downwardly to increase the contact pressure between the contacts 21 and 16 5affurther rise in ambient temperature is required to move the leg portion '23 upwardly until such time as the leg poition 23 physically disconnects the contact 21 from 't-he -cor'itact 16. instantly upon'such disconnection heat- -ing of t-hel'eg portion 22-ceases so that the "leg'portion 22- CTI.

. ture differential of operation to the thermal control de- 'trated in Figure 1.

- predetermined value.

vice.

Upon closing of contact 21 upon contact v16, the light contact pressure occurring at the instant of closing again resultsin high resistance to flow'of current between the contacts and resultant heating of the leg portion'l22 of the bimetal 20. The quick response of the leg portion 22 to the heating effec't'of the contact resistance deflects the leg portion 22 downwardly to increase the contact pressure and thereby prevent reopening of the contacts after the initial closing. This insurespositive closingwof the contacts andelimination of arcing.

In Figure 3 there is illustrated the thermal control device of this invention wherein the bimetal member 20 has the leg portion 23thereof'and the leg portion22 deflected in a manner occurring at the instant of initial contact break between the contact 21 and the contact 16.

The thermal control device illustrated in Figures 1-5 is assembled by first placing the current conducting member 14 and the bimetal member 20 withinthe casing 10 with the formed portions 17 and 121 respectively engaging the end wall 18 of the casing 10. The spacer memher or plug 25 is then inserted between the members 14 and 20 to frictionallyretain them in the position illus- At this time however the initial calibrated break point between contact 21 and contact 16 has not been established.

An apparatus and method to'establish the initial break 'pointsbetween the contact 21 and the contact 16.i's-illustrated inFigure 6. This apparatus comprises a transfer belt 40 having a plurality of sleeves 41 secured therein. The sleeves 41 have flexible fingers 42 adapted to receive and frictionally engage a thermal control device '50.

The transfer belt 40 passes through a chamber 43 that has the temperature thereof controlled internally at a The transfer belt 40 moves the control device 50 positioned thereontoawork-station position at which there is provided a fluid motor 44 and a fluid motor 45 :disposed in alignment. The fluid motor 44 comprises a cylinder 46Lhaving a piston 47 that carries a plunger 48 provided with a'cup shaped member 49 on the end thereof :that isiadaptedtovengage the bottom end of the control device 50 that is moved into alignment with the fluid motor 44. The cup shaped "member 49 has flexible fingers 51 adapted to engage the thermal control device 50.

The fluid motor- 44 has a pressure connection .52 for moving the piston '47 upwardly. -Antinterna12spring 53 in the motor 44 is provided'for. retracting'th'e piston 47 and the plunger '48.

Thefluid motor45compriseslacylinder having a piston 61 provided with a plunger 62 that projects through a guide sleeve 63 of insulating material and is adapted to engage the spacer or plug '25 of the thermal control device 50. Electric spri-n'g'cont'acts 64 and-'65 are provided in the insulating guide sleeve 63 for engagement by the terminal endsl ia and 20a of the-current conducting arm 14 and thebimetal 20 respectively.

The cylinder 60 is supplied with fluid under pressure.

'the" pump '70 is "supplied.

The electrically operated valve 72 has a solenoid actuator 75 that is in series circuit with the spring contacts 64 and 65 and is energized when the thermal control device 50 has the terminals thereof engaging the spring contacts.

A spring 76 is provided to return the piston 60 and thus the plunger 62.

When a thermal control device 50 is moved into alignment with the fluid motors 44 and 45, the fluid motor 44 is supplied with fluid under pressure through the conduit 52 to move the piston 47 upwardly and thus movethe terminal ends 20a and 14a into engagement with the spring contacts 64 and 65. The upward position of the control device 50 relative to the fluid motor 45 is controlled by a stop 80 that engages the end wall 18 of the casing of the control device.

The control device is assembled with the contacts 21 and 16 in closed position. Thus the contacts in the control device 50 close circuit for the valve 72 to provide closing of the valve and thus entrapment of fluid under pressure within the cylinder 60 above the piston 61 to cause the plunger 62 to move downwardly. When the plunger 62 moves downwardly it engages the plug or spacer member 25 to move it longitudinally between the current conducting member 14 and the bimetal member with the forward wall 81 of the plug engaging the angular portion of the bimetal member 20. This forward movement of the plug 25 deflects the bimetal member 20 tending to move the contact 21 away from the contact 16.

Since the operation of moving the plug 25 forwardly into the casing 10 of the control device occurs in a controlled temperature atmosphere at a temperature at which the control switch will normally break contact or circuit through the same, the initial setting of the control device is occasioned under actual operating conditions. Thus the initial break of the contact 21 from the contact 16 will be occasioned under temperature conditions representing actual working conditions with the bimctal '20 free to function under its normal operating conditions heretofore described.

When the plug 25 is moved inward of the casing 10 a suflicient distance to cause the initial break of contact 21 from contact 16, electric circuit will be broken through the electrically controlled valve 72 to immediately stop further advancement of the plunger 62 of the fluid mofor 45. The valve 72 at this time opens to release pressure from above the piston 61 to allow the plunger 62 to return under the action of the spring 76 to its normal position.

Thereafter, pressure is released from the fluid motor 44 to allow return of the piston 47 by the spring 53 and withdrawal of the control device 50 from engagement with the spring contacts 64 and 65 so that the transfer belt 40 can be moved forwardly to place another control device in the work-station.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted as may come within the scope of the claims which follow.

What is claimed is as follows:

1. The method of effecting a predetermined opening point between the contacts of a thermal control device having a pair of longitudinally extending contact carrying arms at least one of which is a bimetallic arm and positioned in spaced fixed relationship at one end thereof with cooperating contacts at the opposite ends, the steps of, eifecting stabilized deflection of the bimetallic arm at a predetermined controlled temperature, establishing a signal current of predetermined value across the said contacts and through said bimetallic arm to heat the arm to normal operating temperature, and inserting a spacer member between the spaced arm ends in frictional engagement therewith and then moving the spacer longitudinally between the arms in engagement with the said one arm .to separate the arms until the contacts on the ends thereof effect initial opening as reflected by a discontinuance of the signal current.

2. The method of effecting a predetermined opening point between the contacts of a thermal control device having a pair of longitudinally extending contact carrying arms at least one of which is a bimetallic arin and positioned in spaced fixed relationship at one end thereof with cooperating contacts at the opposite ends and with one portion of one of the arms at the spaced fixed ends disposed angular to the other arm, efli'ecting stabilized deflection of the bimetallic arm at a predetermined controlled temperature, establishing a signal cur-v rent of predetermined value across the said contacts and through said bimetallic arm, and inserting a spacer member between the spaced arm ends in frictional engagement therewith and then moving the spacer longitudinally between the arms in engagement with the angular portion of the said one arm to separate the arms until the contacts on the ends thereof effect initial opening as reflected by a discontinuance of the signal current.

-3. The method of effecting a predetermined opening point between the contacts of a thermal control device having a contact member and a flexible bimetallic arm positioned with a contact on one end engageable with said contact member and having the opposite end engaging a stop to position the bimetallic arm in operating relationship with said contact member for engagement of the contact on the bimetallic arm with said contact member, the steps of, effecting stabilized deflection of the bimetallic arm at a predetermined controlled temperature, establishing a signal current of predetermined value across the said contacts and through said bimetallic armto heat the arm to normal operating temperature, and then moving an arm position-ing member longitudinally of the bimetallic arm in engagement therewith to flex the arm relative to the contact member until initial opening is effected between the said contact member and the contact on said arm as reflected by a discontinuance of the signal circuit.

4. The method of effecting a predetermined opening point between the contacts of a thermal control device contained in a closed casing having a contact member in a fixed position within the casing and a flexible bimetallic arm positioned in the casing with a contact on one end engageable with said fixed contact member and having the opposite end fixed within the casing to position the bimetallic arm within the casing, the steps of, effecting stabilized deflection of the bimetallic arm at a predetermined controlled temperature, establishing a signal current of predetermined value across said contact, and through said bimetallic arm to heat the arm to normal operating temperature, and then moving an arm po sitioning member longitudinally of the bimetallic arm in engagement therewith to flex the arm relative to the contact member until initial opening is effected between the said contact member and the contact on said arm as reflected by a discontinuance of the signal current.

5. The method of effecting a predetermined opening point between the contacts of a thermal control device contained in a closed casing having a contact member in a fixed position within the casing and a flexible bimetallic arm positioned in the casing with a contact on one end engageable with said fixed contact member and having the opposite end fixed within the casing to position the bimetallic arm within the casing with the contact on the bimetallic arm in cooperating engagement with said fixed contact and having an angular portion at the fixed end thereof, the steps of, inserting a closure plug member into one end of the casing to close the same and in frictional engagement with said bimetallic arm to retain the fixed end thereof in position in said casing, establishing a signal circuit of predetermined value across the contacts of the control device and through said bi- :ga'gementwtith mhez angular pontionthereof to flexthe -amn 're1ative -to tbe 'contact member until the signal circuit si'gnals'finitial openingtof'the said contacts and concurrently therewith and in response thereto :stopping movement Of the plugirelative to the bimetallic arm whereby to fix the opening :point of the contact.

References Citedfiin the file -of-.this patent "UNITED STATES PATENTS Rabezzana Mar. 8, GetcheIl Dec. 4, .Beman i J an. 7:26, Winckler May 10, Harris July 8, .Pa'shby v l -Dec. 6,

as. m: 

